As if it were a separate second brain, as recent mouse studies show:
Our huge gastrointestinal tracts operate their own nervous system, using neurons that follow different principles from those of brain neurons, according to recent findings:
“Our approximately seven-meter long gastrointestinal (GI) tract has its own functionally distinct neurons. Since this enteric nervous system (ENS) operates autonomously, it is sometimes referred to as the “second” or “abdominal” brain. While the ENS controls muscle movement (peristalsis) in the gut and its fluid balance and blood flow, it also communicates with the immune system and microbiome. Karolinska Institutet, “New Fundamental Knowledge of the ‘Abdominal Brain’” at Medical Xpress (December 7, 2020) Paper. (Subscription Required)” The Karolinska researchers made progress in studying the little-understood second brain by mapping the neuron types in the digestive systems of mice. The human gut is estimated to contain an independent network of over 100 billion neurons that not only control digestion but work with the immune system to fight a constant war with hostile bacteria.News, “Did you know you have a second brain?” at Mind Matters News
In humans, the abdominal brain is thought to play a role in emotion, though not in reason or moral choice.
It would be interesting to know if the abdominal brain dates back to the Cambrian.